Ferris, CP

Gordon, AW

McDonald, EJ

McRoberts, WC

Pourshahidi, LK

English

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Important notes:Do NOT enter author and affiliation information on this document. You will be able to enter this information online when you submit the abstract.Do NOT write outside the boxes. Any text or images outside the boxes will be deleted.Do NOT alter the structure of this document. Simply enter your title and abstract in the gray boxes. The document will be automatically processed – if you alter its structure your submission will not be processed correctly.Title: (Use Normal style (Times New Roman 12). Only capitalise the first letter of the first word.  No full stop at the end of the title)The impact of three contrasting dairy cow management strategies on the vitamin D content of milkSummary:  (Your summary (Times New Roman 10) must use Body text  style and must not be longer than this box)Application  Housed dairy cows offered either fresh grass or grass silage produce milk with lower concentrations of vitamin D than grazing cows. This highlights the need to develop strategies to increase vitamin D concentrations in the milk of housed cows.Introduction Humans obtain Vitamin D through endogenous dermal synthesis upon exposure to UVB light, from naturally occurring food sources, and from supplements and fortified food products.  However, Vitamin D deficiency is well recognised as a public health issue, with recent research (Cashman et al., 2016) suggesting that 40.4% of the EU population is Vitamin D deficient.  While oily fish and eggs represent good naturally occurring sources of Vitamin D, these are not widely consumed.  In addition, people living at more northerly latitudes have limited Vitamin D synthesis for a considerable part of the year. Consequently, there is interest in increasing the Vitamin D content of more commonly consumed foods, such as milk.  This study investigates the effect of dairy cow management regime on Vitamin D concentrations in milk.Material and methods Three management strategies were examined in a 24-week (April – September), continuous design experiment involving 114 Holstein Friesian dairy cows (38 cows/strategy), as follows: i. housed and offered grass silage (Silage), ii. housed and offered fresh grass (Zero-grazing), iii. full-time grazing (Grazing). Concentrate feed levels were common across all three treatments (8.0 and 6.0 kg/day for multiparous and primiparous cows, respectively).  Cows within the Silage and Zero-grazing treatments were housed in cubicle accommodation.  These cows were offered either fresh silage or fresh herbage once daily. Cows on treatment Grazing were managed within a rotational paddock grazing system, and given access to fresh herbage daily.  On two occasions during the experiments (6 July and 20 September) milk samples were taken from all cows during two consecutive milkings, bulked in proportion to milk yield, and the samples subsequently analysed for vitamin D3, vitamin D2, 25-hydroxyvitamin D3 (25-(OH)-D3) and 25-hydroxyvitamin D2 (25-(OH)-D2).  Data were analysed with linear mixed model methodology using the REML estimation method. A factorial arrangement of management and date were fitted as fixed effects with cow fitted as a random effect.Results Both management strategy and sampling date had a significant effect on vitamin D3, D2 and 25-(OH)-D3 concentrations (P<0.001).  Compared to Silage and Zero grazing, milk from Grazing had higher mean concentrations of vitamin D3 and its metabolite 25-(OH)-D3 on both sampling dates, and higher vitamin D2 concentrations on the first sampling date. Management strategy x date interactions were observed for vitamins D3 and D2 (P<0.001) but not 25-(OH)-D3. Concentrations of 25-(OH)-D2 were below the detection limit in all samples.Table 1 Effect of management strategy on milk production and the Vitamin D content of milk during the two measurement periodsDateTreatmentSEMSignificanceZerograzingSilageGrazingManagement (M)Date (D)M x DVitamin D3(µg/kg)6 July0.037a0.040a0.203c0.0094<0.001<0.001<0.00120 Sep0.041a0.036a0.088bVitamin 25-(OH) D3 (µg/kg)6 July0.058a0.058a0.094d0.0036<0.001<0.001NS20 Sep0.048 b0.049 b0.082cVitamin D2(µg/kg)6 July0.021ab0.022 ab0.046c0.0024<0.001<0.001<0.00120 Sep0.026b0.018a0.018aValues within each variable which do not share the same superscript are significantly different (p<0.05) as determined by Fishers LSD test.Conclusion Housed cows, irrespective of diet, produced milk with lower concentrations of Vitamin D3 and 25-(OH)-D3 than grazing cows.  With grazing cows, Vitamin D concentrations were significantly lower in September than July.Acknowledgements: This study was co-funded by the Agri-Food Quest Competence Centre (AFQCC) and carried out in partnership with Devenish Nutrition, AFBI, Thompsons, Dale Farm, Karro, CAFRE and Ulster University.References Cashman, K.D. et al. 2016. American Journal for Clinical Nutrition. 103, 1033–44.

The impact of three contrasting dairy cow management strategies on the vitamin D content of milk

https://pure.ulster.ac.uk/ws/files/11656842/BSAS2018_0047.doc

The impact of three contrasting dairy cow management strategies on the vitamin D content of milk

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